Novel gene therapy could reduce bleeding risk for haemophilia patients

A single gene therapy injection could dramatically reduce the bleeding risk faced by people with haemophilia B, finds a study involving UCL researchers.

For the paper, published in the New England Journal of Medicine, experts from UCL, Royal Free Hospital and biotechnology company Freeline Therapeutics trialled and continue to evaluate a new type of adeno-associated virus (AAV) gene therapy candidate, called FLT180a, to treat severe and moderately severe cases of the condition.

Haemophilia B is a rare and inherited genetic bleeding disorder caused by low levels of the factor IX (FIX) protein, needed for forming blood clots that help prevent or stop bleeding. The gene responsible for making FIX protein is located on the X chromosome, so the severe form of haemophilia B is much more common in men.

Currently, patients with haemophilia B need to inject themselves regularly — usually weekly — with recombinant FIX, i.e. regular replacement therapy to prevent excessive bleeding. Despite advances in treatment, patients may continue to see debilitating joint damage.

The Phase I/II multi-centre clinical trial, called B-AMAZE, and the related long-term follow up study found that one-time treatment with FLT180a led to sustained production of FIX protein from the liver in nine of ten patients, across four different dose levels, removing the need for regular replacement therapy.

Out of 17 male patients aged 18 or over who underwent screening, ten with severe or moderately severe haemophilia B took part in the 26-week trial of FLT180a. They are also all enrolled in the long-term follow up study to assess safety and durability of FIX expression for 15 years.

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